2. What is a Sensor?
A device that measures a physical variable (e.g.
force, pressure, temperature, velocity, flow rate,
And converts the physical quantity into another
Which can be read by an observer or by an
The most common conversion is to electrical form
as the converted signal is more convenient to use
3. General Electronic Sensor
• Primary Transducer: changes “real world” parameter into electrical signal
• Secondary Transducer: converts electrical signal into analog or digital
Typical Electronic Sensor System
4. Desirable features of sensors
Speed of response
Cost and ease of operation
10. Where is the face?
Face detection & tracking
Why Sensors are Required?
11. Sensors used in Robotics
The sensors used in robotics include a wide range of
devices which can be divided into following categories:
Proximity and Range sensors
Miscellaneous sensors and sensor based
Machine vision systems
12. Tactile Sensors
Tactile sensors are devices which indicate contact
between themselves and some other solid object.
Tactile sensing devices can be divided into two
classes: Touch sensors and Force sensors.
14. Force Sensing
• Force sensor (also known as stress sensor)
indicate not only that contact has been made
with the object but also the magnitude of the
contact force between the two objects.
Metal foil strain-gauge based (load cell)
Good in low frequency response
High load rating
Resolution lower than piezoelectricity-based
Rugged, typically big size, heavy weight
15. Force Sensing
Piezoelectricity based (force sensor)
lower cutoff frequency at 0.01 Hz
can NOT be used for static load measurement
Good in high frequency
Limited operating temperature (can not be
used for high temperature applications)
Compact size, light
16. Proximity and Range Sensors
Proximity sensors are devices that indicate when
one object is close to another object.
Some of these sensors can also be used to measure
the distance between the object and the sensor, and
these devices are called Range sensors.
Range sensors would be useful for determining the
location of an object(e.g., the work part) in relation
18. Eddy Current Detector
device that emits an alternating magnetic field
at the tip of a probe, which induces eddy
currents in any conductive object in the range
of the device.
19. Photometric sensor
used to sense light. category includes photocells ,
photoelectric transducers ,photo tubes,
phototransistor and photoconductors. Can be used
to indicate presence or absence of an object.
20. Optical Pyrometer
device used to measure high temperatures by
sensing the brightness of an object’s surface.
Can be used to indicate presence or absence of
21. Vacuum Switches
device used to indicate negative air pressures.
Can be used with a vacuum gripper to indicate
presence or absence of an object.
22. Miscellaneous Sensors and Sensor
The miscellaneous category covers the remaining
types of sensors that might be used for interlocks
and other purposes in manufacturing work cells.
This category includes devices with the capability
to sense variables such as temp., pressure, fluid
flow, and electrical properties.
23. Types of Miscellaneous Sensor
• Ammeter: Electrical meter used to measure electrical
• Linear variable differential transformer:
Electromechanical transducer used to measure linear
or angular displacement.
• Ohmmeter: used to measure electrical resistance.
• Potentiometer: Electrical meter used to measure
24. Types of Miscellaneous Sensor
• Piezoelectric accelerometer: sensor used to indicate or
• Pressure transducer: Various transducers used to
indicate air pressure and other fluid pressures.
• Thermistor : device based on electrical resistance used
to measure temperatures.
• Thermocouple: used to measure temperatures. Based
on the principle that a junction of two dissimilar metals
will emit an emf which can be related to temperatures.
25. Machine Vision System
Vision sensors: Advanced sensor system used
together with pattern recognition and other
techniques to view and interpret events
occuring in the robot workplace.
26. Magnetic Field Sensor
Magnetic Field sensors
are used for power
steering, security, and
on transmission lines
Hall voltage is
x x x x x x
x x x x x x
x x x x x x
+ + + + + + + + + + + + + + +
- - - - - - - - - - - - - - -
I (protons) +
27. Ultrasonic Sensor
Ultrasonic sensors are used
for position measurements
Sound waves emitted are in
the range of 2-13 MHz
Sound Navigation And
Radio Detection And
Ranging (RADAR) –
15° - 20°
28. Applications of Sensors in
Machine Vision / Pattern recognition
Process Parameter sensing
Parts inspection for quality control
29. Distance Sensing
• Sensors for such application are of two types,
either contact type or non contact type.
•Contact type sensors are like dial gauge, gauge
blocks, pins, etc. However these sensors have a
limitation of wear and tear, and are not very
•Non contact types may be inductive, acoustic,
capacitive or optical sensors.
30. Contour tracking:
This is a kind of scanning process and is performed
by using electrical sensors such as inductive and
capacitive ones and optical sensors mostly laser
Here also tactile arrays and ultrasonic scanning
serve some useful purpose. Besides optical systems
with binary vision, grey level sensing and
stereovision are widely used.
31. Machine Diagnosis:
Well known sensors are used to measure forces,
torque, strain, frequency and a lot of other
indirect diagnostic data.
Process Parameters Monitoring:
Parameters such as pressure, force, speed,
temperature, fluid levels, chemical composition
and pH value data are measured in different